It is generally desirable to create integrated circuits that have clock signals that are aligned with each other to maintain synchrony across various components on the circuit. Often, systems may use multiple clock signals that have frequencies that are related to one another. For example, a system may use a first clock signal at a first frequency and a second clock signal at a second frequency that is an integer multiple (e.g., 2×, 3×, 4×, or any other suitable number) of the first frequency.
A phase detector or a phase frequency detector may be used in a phase locked loop (PLL), and may be used to measure a difference in phase between two input signals. These require careful design and control of their physical implementation. Often, a PLL is placed on a separate chip from other components. The signals to and from the PLL often have to travel a long distance, and variation along the signal path causes increased loss of the useful portion of the clock cycle.
Moreover, field-programmable gate arrays (FPGAs) sometimes have limited clock generation options, and clock signals in an FPGA sometimes require being routed a long distance on the integrated circuit before being distributed to the subsystem that makes use of the clock signals. This long distance causes and exacerbates an uncertainty between related clock signals when they arrive at the subsystem. This effectively reduces the remaining useful clock period.